The present invention is specific to an improved method of treating corn stillage. More specifically, the present invention is specific to improvements in the yield of corn oil from ethanol production facilities. Even more specifically, the present invention is related to modifications of corn oil to increase the extraction of value added components of corn stillage.
The production of ethanol from corn has increased significantly due, at least in part, to the use of ethanol as a motor fuel. This increase has led to ever increasing efforts to improve yields and, particularly, to improve the extraction of marketable products from the process. In general, there are several commercial products achieved from ethanol production with ethanol being a primary product. The secondary products of value are corn oil and dry distiller grain (DDG). Corn oil has many commercial applications, such as an additive in food stuffs, and DDG is a valuable feed for livestock. The relative value of corn oil exceeds the relative value of DDG and therefore it is advantageous to increase the corn oil yield which is otherwise incorporated in the DDG without appreciative value being added to the DDG.
The overall process is well known to include the mixture of corn with water to form mash. Enzymes are then added to convert the corn starch to sugar after which the sugar is converted to ethanol by fermentation thereby forming an intermediate referred to in the art as “beer”. The ethanol is extracted from the beer by distillation with the remaining portion being referred to as stillage. The stillage contains water, protein, nutrients, fiber, and corn oil. It is preferable to remove the corn oil from the stillage with the fraction remaining being dried and provided commercially as DDG.
Separation of the corn oil and DDG typically involves an initial step of centrifugation wherein the solids fraction is referred to as wet grain and the liquid, which contains the corn oil, is referred to as thin stillage. The water of the thin stillage is reduced, preferably by evaporation with the water preferably being recycled into the process, resulting in syrup which has a higher concentration of corn oil than the thin stillage. The syrup and corn oil are then separated, again preferably by centrifugation, with the corn oil being isolated and the remainder, or oil depleted syrup, preferably being reincorporated with the wet grain. The wet grain is then typically dried for use as, primarily, dry feed. There has been significant effort in the art focused on increasing the amount of corn oil extracted from the stillage. The theoretical yield of corn oil per bushel of processed corn is about 725.7 grams (1.6 pounds) yet this theoretical limit is not met leading to the desire for processes and methods to increase the yield of corn oil.
U.S. Pat. No. 8,841,469, which is incorporated herein by reference, utilizes functionalized polyols derived from sorbitol, a sorbitan or isosorbide as a chemical additive to the process steam. Though beneficial, the yield is still well below the theoretical yield thereby leading to the desire for further improvements.
The present invention provides a significant improvement in the extraction of corn oil from corn stillage by chemical modification of corn oil and further formation of a derivative of the modified corn oil. The result is an increase in yield of corn oil without compromising the value of DDG. It would be understood to those of skill in the art that methods for increasing corn oil yield which render the DDG unsuitable for use as feed for livestock would be financially unsuitable solutions.